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Toxicity of Combined Chlorine Residuals to Freshwater Fish
John A. Zillich
Journal (Water Pollution Control Federation)
Vol. 44, No. 2 (Feb., 1972), pp. 212-220
Published by: Water Environment Federation
Stable URL: http://www.jstor.org/stable/25037299
Page Count: 9
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On-site continuous-flow bioassays on fathead minnows using chlorinated and dechlorinated effluents from two treatment plants have shown residual chlorine to be the principal toxic agent in these effluents. The toxic effects at both locations were similar, in spite of the fact that one plant received metal-finishing wastes and the other did not; in both cases, the pH and dissolved oxygen concentration were favorable for fish life. The residual chlorine concentrations that produced a 100 percent kill was 0.16 and 0.21 mg/l; threshold concentrations were 0.04 and 0.05 mg/l. The addition of sodium thiosulfate to both effluents removed the residual chlorine and rendered them nontoxic.
Journal (Water Pollution Control Federation) © 1972 Water Environment Federation